The present invention relates to gate valves and more particularly to a novel gate for use in the valve having passages for flushing scale material from a valve housing back into a flow stream. In addition, the present invention is directed to a novel shell core use in fabricating a gate port and a method of making the shell core.
Gate valves having through ports are commonly used in conjunction with fluid conducting pipes in order to regulate fluid flow therethrough. A typical gate valve includes a housing within which a gate is operable for selective shifting to present either the port or an obstruction to fluid flow. It is known that continued use of a gate valve may result in an accumulation of corrosive particles such as sand or scale between upstream and downstream faces of the gate and corresponding walls of the housing. The accumulation of particles may result in impaired operation of the gate valve. It has therefore been proposed to mount a "scale ring" within marginal sand grooves on the upstream and downstream faces of the gate for sliding contact with the walls of the housing. The sliding contact results in an abrading or scraping off of the particles into cavities between the scale ring and a bottom portion of the grooves.
In order to transfer or flush the accumulated particles back into a fluid flow for downstream removal, it has been proposed to provide passages extending from the peripheral wall of the gate's through port into the cavities where the particles have accumulated. Fluid flow through the port tends to create a partial vacuum adjacent the opening of the passages into the port thereby drawing the particles upwardly for discharge into the fluid stream.
However, a problem exists in fabricating the passages in a gate. For instance, the prior art contemplates drilling of the passages in a gate which has already been cast. Unfortunately, it is generally not possible to drill passages so that they extend radially outwardly from the cylindrical axis to the grooves. This is because ports generally are not sized sufficiently large enough to permit insertion of a drill for boring. As a consequence, boring or drilling must be directed at an angle which results in a longer passage inclined relative the peripheral wall of the port in a nonradial direction.
Accordingly, it is a general object of the present invention to provide a gate for use in a gate valve in which the gate includes passages extending in a radial direction from the cylindrical axis of the port to the grooves. This results in the passages having their longitudinal axes perpendicular to liquid flow and the effect is greater turbulence adjacent the opening of the passages into the cylindrical wall of the port. The turbulence results in a greater vacuum being produced thereby facilitating flushing out of the particles from the bottom of the grooves.
Another object of the present invention is to provide a shell core of novel construction which may be advantageously employed in the casting of a gate. The shell core includes core body sections each including elongate projections which, when mounted in gate molds, will enable the casting of a gate having the radially extending passage construction as described above.
Still another object of the present invention to provide a novel core box construction for fabricating the shell core described above.
These and additional objects and advantages of the present invention will become more readily apparent from a consideration of the drawings and the following detailed description of the preferred embodiments.